Influence of ingredient particle size and inclusion level of pre-gelatinised maize starch on apparent digestibility coefficients of diets in South African abalone ( Haliotis midae L.)

Abstract

The influence of ingredient particle size on dry matter leaching and apparent digestibility coefficients (ADCs) in Haliotis midae (56.49±0.12 mm shell length; 35.60±0.24 g live weight, mean±S.E.) was evaluated by including soybean meal sieved to three different particle sizes (<150, 150–450 and 450–1000 μm) in diets. Acid-insoluble ash (AIA) was used as marker in digestibility studies. No differences ( P>0.05) were found in dry matter leaching and apparent digestibility of dry matter, organic matter, protein and fat between ingredient particle sizes of <150 and 150–450 μm. However, an ingredient particle size of 450–1000 μm increased ( P<0.05) dry matter leaching and decreased ( P<0.05) apparent digestibility. In a second experiment, pre-gelatinised maize starch was included in experimental diets at 20%, 30%, 40% and 50% replacing α-cellulose fibre. No influences ( P>0.05) on apparent digestibility of protein, fat, fiber and starch were observed among diets; however; apparent dry matter, organic matter, energy and nitrogen-free extract digestibility increased linearly ( P<0.05) as inclusion level of dietary pre-gelatinised maize starch increased. A relatively high apparent digestibility (>60%) of fibre was observed, indicating a need for further studies to quantify the effect of the sources and type of fibre on its digestibility.